Remove navigation back button after user logout

Question

I'm using Android Jetpack Navigation Component for my app. It has Two screen (Fragment) which are homeFragment and loginFragment. The homeFragment is the start destination. After logout from homeFragment to loginFragment, the navigation back button shows up, it will back to homeFragment again when click, that's not correct. I expect the back button not shown in loginFragment, and if user press system back app exit. The nav_graph.xml is setting properly as this post was told:

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_graph"
    app:startDestination="@id/homeFragment">

    <fragment
        android:id="@+id/loginFragment"
        android:name="cn.helptool.qxscales.LoginFragment"
        android:label="Login" >
        <action
            android:id="@+id/action_loginFragment_to_homeFragment"
            app:destination="@id/homeFragment"
            app:popUpTo="@id/nav_graph"
            app:popUpToInclusive="true" />
    </fragment>
    <fragment
        android:id="@+id/homeFragment"
        android:name="cn.helptool.qxscales.HomeFragment"
        android:label="Home">
        <action
            android:id="@+id/action_homeFragment_to_loginFragment"
            app:destination="@id/loginFragment"
            app:popUpTo="@id/nav_graph"
            app:popUpToInclusive="true" />
    </fragment>
</navigation>

Answer 1

After read android docs

Add both of loginFragment and homeFragment as top level destinations, the problem fixed.

val appBarConfiguration = AppBarConfiguration.Builder(R.id.loginFragment, R.id.homeFragment).build()
setupActionBarWithNavController(navController, appBarConfiguration)